Many earth-working machines, such as, for example, loaders, graders, and excavators, include operator-compartments with heating, ventilation, and/or air conditioning systems (“HVAC systems”). Such systems typically supply an operator-compartment with a mix of air from outside of the compartment (i.e., outside air) and air from inside of the compartment (i.e., recirculated air). Since the outside air and the recirculated air may include various unwanted materials (e.g., dust particles), the systems often include filters for filtering out such materials.
U.S. Pat. No. 4,410,427 to Wydeven discloses an exemplary filter pack including alternating flat and corrugated layers of filter media. The combination of flat and corrugated layers creates hollow passages (i.e., flutes) in each of the corrugated layers. The corrugated layers of filter media on either side of each flat layer of filter media are oriented such that their corrugations (and flutes) are substantially orthogonal to each other. Fluids may enter a first set of the flutes through opposing entry sides of the filter pack, pass through the flat layers of filter media into a second set of flutes oriented substantially orthogonal to the first set of flutes, and exit the second set of flutes through opposing exit sides of the filter pack, which are oriented substantially orthogonal to the entry sides of the filter pack.
The filter pack of the '427 patent may provide certain benefits in some applications. However, it may have certain drawbacks. For example, although the opposing entry sides of the filter pack may allow two different fluids to enter the filter pack, the fluids would mix in the filter pack and thus be filtered by the same filter media. As a result, it might not be possible to tailor the filter media to the different fluids being filtered. For example, in an HVAC system for an operator-compartment, it may be desirable to subject outside air to more stringent filtering than recirculated air. Accomplishing this might require the use of two of the filter packs of the '427 patent, one for the outside air and one for the recirculated air, increasing both the space required in the compartment for the filters and the maintenance time associated with changing the filters. The disclosed embodiments may help solve these problems.